mpi - 数据传输问题 : MPI_Isend followed by MPI_Probe and MPI_Recv

Question

我有以下代码

int main(int argc, char* argv[])
{
    int rank, size;

    MPI_Init (&argc, &argv);    
    MPI_Comm_rank (MPI_COMM_WORLD, &rank);  
    MPI_Comm_size (MPI_COMM_WORLD, &size);  

    MPI_Request mpiRequest;
    MPI_Status myStatus;
    int tag = 11;


    int testData = 12;
    MPI_Isend(&testData,1,MPI_INT,(rank+1)%size,tag,MPI_COMM_WORLD,&mpiRequest); 
    MPI_Wait (&mpiRequest,&myStatus);

    int source = (rank+size-1)%size;
    int sizeProb = MPI_Probe(source,tag,MPI_COMM_WORLD,&myStatus);
    int * recvTransferArray = new int [sizeProb];

    MPI_Recv(recvTransferArray,sizeProb,MPI_INT,source,tag,MPI_COMM_WORLD,&myStatus);

    MPI_Finalize();

    return 0;
}

问题是在 sizeProb 中我得到 0，我应该得到 1。

我可以使用 MPI_ISend 发送数据并使用 MPI_Probe/MPI_Recv 组合接收数据吗？

Answer 1

事实sizeProb永远是0是件好事! MPI_Probe()返回一个错误代码，意思是 MPI_SUCCESS在你的情况下。要检索其他进程发送的数组的大小，您可以使用 MPI_Get_count(&myStatus, MPI_INT, &sizeProb);
两个链接:

示例 http://mpitutorial.com/dynamic-receiving-with-mpi-probe-and-mpi-status/

MPI_Get_count() http://www.mpich.org/static/docs/v3.1/www3/MPI_Get_count.html

这是一个基本示例:

#include "mpi.h"

int main(int argc, char* argv[]) { int rank, size;

  MPI_Init (&argc, &argv);    
  MPI_Comm_rank (MPI_COMM_WORLD, &rank);  
  MPI_Comm_size (MPI_COMM_WORLD, &size);  

  MPI_Request mpiRequest;
  MPI_Status myStatus;
  int tag = 11;


  int testData = rank;
  MPI_Isend(&testData,1,MPI_INT,(rank+1)%size,tag,MPI_COMM_WORLD,&mpiRequest); 
  MPI_Wait (&mpiRequest,&myStatus);

  int source = (rank+size-1)%size;
  MPI_Probe(source,tag,MPI_COMM_WORLD,&myStatus);
  int sizeProb;
  MPI_Get_count(&myStatus, MPI_INT, &sizeProb);
  int * recvTransferArray = new int [sizeProb];

  MPI_Recv(recvTransferArray,sizeProb,MPI_INT,source,tag,MPI_COMM_WORLD,&myStatus);
  std::cout<<"proc "<<rank<<" received "<<sizeProb<<" int, first being "<<recvTransferArray[0]<<std::endl;
  MPI_Finalize();

  return 0;

}